1. Field of the Invention
The subject invention is directed to vascular introducers, and more particularly, to a hemostasis valve for vascular introducers that provides a complete hemostatic seal regardless of the diameter of the object introduced through the valve, while exhibiting lower insertion and extraction forces than prior-art hemostasis valves.
2. Description of Related Art
The percutaneous introduction of diagnostic and therapeutic devices such as pacemaker leads and cardiovascular catheters into a blood vessel is typically accomplished with the aid of an introducer assembly. Introducer assemblies generally include a dilator having a tapered end portion and a thin-walled introducer sheath having a lumen extending through the sheath to initially accommodate the dilator, and subsequently accommodate the passage of a pacemaker lead or catheter.
Typically, the percutaneous introduction of an introducer assembly is accomplished by first inserting a needle into the blood vessel at a desired location and verifying its position by observing fluid return or by a similar method. While the needle is held firmly in place, a guidewire is inserted through the needle cannula to the desired depth. The guidewire is then held in place and the needle is withdrawn. Pressure is applied on the puncture site to minimize blood loss. Next, the introducer assembly is threaded over the guidewire. The introducer assembly is grasped close to the skin surface and advanced through the tissue to the desired position. Then, the dilator and guidewire are removed, leaving the sheath installed. A lead, catheter, or similar diagnostic or therapeutic device is then introduced into the sheath and advanced to the desired position. Lastly, the sheath is removed, leaving the device disposed within the blood vessel.
It is known to configure an introducer sheath so that it may be easily removed or separated from the lead or catheter after it has been put in place. For example, it is known to provide score lines in the wall of the sheath to enable the sheath to be peeled away, slit, or split open. Once the sheath has been removed and catheter has been put in place, therapeutic medical devices such as endocardial pacing/defibrillation leads may be introduced into the blood vessel through the catheter.
Once the sheath has been inserted into a blood vessel, it provides a passage for the free flow of blood. This may result in significant blood loss from a patient. The sheath also provides an open passage for the introduction of air into the blood vessel, which could cause an embolism in the vascular system of the patient. To overcome these problems, vascular introducers have been developed with hemostatic valves that prevent the free flow of blood through the introducer sheath.
Examples of such devices are disclosed in U.S. Pat. No. 4,798,594 to Hillstead, U.S. Pat. No. 5,125,904 to Lee and U.S. Pat. No. 5,409,463 to Thomas et al., the disclosures of which are incorporated herein by reference in their entireties. In each of these devices, the hemostatic valve is configured to create frictional resistance to the passage of therapeutic devices such as flexible cardiac leads. This makes introduction of a lead difficult and can actually cause damage to the lead.
There is a need for a hemostasis valve for a vascular introducer that effectively prevents the backflow of blood and other fluids while exhibiting lower insertion and extraction forces than prior-art hemostasis valves.